| Project/Area Number |
02650509
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
金属材料(含表面処理・腐食防食)
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| Research Institution | IBARAKI University |
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Principal Investigator |
TOMOTA Y. IBARAKI University, Faculty of Engng. Professor, 工学部, 教授 (90007782)
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| Project Period (FY) |
1990 – 1991
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| Project Status |
Completed (Fiscal Year 1991)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1991: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1990: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Keywords | Martensitic Transformation / Shape Memory / Cyclic Transformation / High Mn Ferrous Alloy / Epsilon Martensite / Two-way Shape Memory |
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| Research Abstract |
The effect of austenite (gamma) - epsilon martensite (epsilon) transformation on deformation behavior was investigated by using Fe-24Mn, Fe-24Mn-6Si and Fe-26Mn-6Co alloys. The recovery process of reversely-transformed gamma was studied. The effect of chemical compositions and the upper temperature of cyclic heating on two way shape memory was examined.
It is found that the forward and reverse transformations in 24Mn-6Si are reversible, while it is not and gamma is stabilized in 24Mn by repeated gamma - epsilon cyclic transformations. The stabilization and enhancement of the yieled strength of gamma is recognized due to the cyclic heating and cooling in 24Mn. On the other hand, 24Mn-6Si exhibits microstructural memory, shows a little increase in the amount of epsilon and shows a slight increase of 0.2% proof stress, due to the thermal cycles. Tensile deformation behaviors in 24Mn and 24Mn-6Si are affected by the upper temperature of heating. The effect of test temperature on 0.2% proof
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stress in reversely transformed gamma was examined.
The epsilon -> gamma reversion behavior in 24Mn-6Si is quite different from that in 24Mn. The 0.2% proof stress after one or 10 cycles is decreased by heating up to 1273K in 24Mn. The 0.2% proof stress on recrystalized gamma is lower than that of reversely-transformed one. The epsilon -> gamma transformation is believed to introduce dislocations in reversely transformed gamma.
A large elongation in specimens slightly plastically deformed at 523 K is found during the cooling under the applied stress. The difference in the reversion between thermally-induced epsilon and stress-induced one is very large. It is found that large shape memory in 24Mn-6Si but not in 24Mn. When the stress-induced epsilon is first introduced and then heated and cooled repeatedly, two way shape memory is found. When 873K is employed as the upper temperature of the heating, cyclic shape change is not observed. The effect of the upper heating temperature on the two way shape memory is consistent with that on the microstructural memory. Less
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